package gui;

import java.awt.event.*;
import javax.swing.*;
import java.beans.*;

/*
 * This class listens for changes made to the data in the table via the
 * TableCellEditor. When editing is started, the value of the cell is saved
 * When editing is stopped the new value is saved. When the oold and new
 * values are different, then the provided Action is invoked.
 *
 * The source of the Action is a TableCellListener instance.
 */
public class TableCellListener implements PropertyChangeListener, Runnable {

    private JTable table;
    private Action action;
    private int row;
    private int column;
    private Object oldValue;
    private Object newValue;

    /**
     * Create a TableCellListener.
     *
     * @param table the table to be monitored for data changes
     * @param action the Action to invoke when cell data is changed
     */
    public TableCellListener(JTable table, Action action) {
        this.table = table;
        this.action = action;
        this.table.addPropertyChangeListener(this);
    }

    /**
     * Create a TableCellListener with a copy of all the data relevant to the
     * change of data for a given cell.
     *
     * @param row the row of the changed cell
     * @param column the column of the changed cell
     * @param oldValue the old data of the changed cell
     * @param newValue the new data of the changed cell
     */
    private TableCellListener(JTable table, int row, int column, Object oldValue, Object newValue) {
        this.table = table;
        this.row = row;
        this.column = column;
        this.oldValue = oldValue;
        this.newValue = newValue;
    }

    /**
     * Get the column that was last edited
     *
     * @return the column that was edited
     */
    public int getColumn() {
        return column;
    }

    /**
     * Get the new value in the cell
     *
     * @return the new value in the cell
     */
    public Object getNewValue() {
        return newValue;
    }

    /**
     * Get the old value of the cell
     *
     * @return the old value of the cell
     */
    public Object getOldValue() {
        return oldValue;
    }

    /**
     * Get the row that was last edited
     *
     * @return the row that was edited
     */
    public int getRow() {
        return row;
    }

    /**
     * Get the table of the cell that was changed
     *
     * @return the table of the cell that was changed
     */
    public JTable getTable() {
        return table;
    }
//
// Implement the PropertyChangeListener interface
//

    @Override
    public void propertyChange(PropertyChangeEvent e) {
        // A cell has started/stopped editing
        if ("tableCellEditor".equals(e.getPropertyName())) {
            if (table.isEditing()) {
                //System.out.printf("tableCellEditor is editing..%n");
                processEditingStarted();
            } else {
                //System.out.printf("tableCellEditor editing stopped..%n");
                processEditingStopped();
            }
        }
    }

    /*
   * Save information of the cell about to be edited
     */
    private void processEditingStarted() {
        // The invokeLater is necessary because the editing row and editing
        // column of the table have not been set when the "tableCellEditor"
        // PropertyChangeEvent is fired.
        // This results in the "run" method being invoked
        SwingUtilities.invokeLater(this);
    }

    /*
   * See above.
     */
    @Override
    public void run() {
        row = table.convertRowIndexToModel(table.getEditingRow());
        column = table.convertColumnIndexToModel(table.getEditingColumn());
        oldValue = table.getModel().getValueAt(row, column);
        //这里应对oldValue为null的情况做处理，否则将导致原值与新值均为空时仍被视为值改变
        if (oldValue == null) {
            oldValue = "";
        }
        newValue = null;
    }

    /*
   *  Update the Cell history when necessary
     */
    private void processEditingStopped() {
        newValue = table.getModel().getValueAt(row, column);
        //这里应对newValue为null的情况做处理，否则后面会抛出异常
        if (newValue == null) {
            newValue = "";
        }
        // The data has changed, invoke the supplied Action
        if (!newValue.equals(oldValue)) {
            // Make a copy of the data in case another cell starts editing
            // while processing this change
            TableCellListener tcl = new TableCellListener(
                    getTable(), getRow(), getColumn(), getOldValue(), getNewValue());
            ActionEvent event = new ActionEvent(
                    tcl,
                    ActionEvent.ACTION_PERFORMED,
                    "");
            action.actionPerformed(event);
        }
    }
}
